Packaging devices of conventional structure are known, these comprising a container on which a manual pump for dispensing the product contained in the container is fitted. A pump of this type generally includes a plunger making it possible, through simple pressure from the user's finger, to cause the displacement of a piston in a pumping chamber, the volume of which determines the metered amount to be dispensed. A first valve makes it possible to isolate this chamber from the inner volume of the container, when the product is expelled from this chamber via a second valve, through the effect of the displacement of the piston through pressure on the plunger, and the second valve makes it possible to isolate the chamber from the outside, when this chamber is filled via the first valve with a metered amount of product originating from the inside of the container and sucked into the chamber by means of the return of the piston towards its initial position, pressing against a stop of a pump body in which the piston slides, and through the action of elastic return means.
Therefore, each time the piston returns to its initial position, obtained through the effect of the elastic return means, such as a spring, a metered amount of product is sucked into the chamber of the pump.
This suction of the product gives rise to a reduced pressure inside the container.
In order to prevent outside air from penetrating into the container in order to offset this reduced pressure, packaging and dispensing devices have been proposed which include a pump without air intake, as well as a deformable container, which contains the product to be packaged and dispensed. Each time a metered amount of product is expelled from the deformable container, the reduced pressure created contracts this deformable container around which a rigid outer container has been provided to afford mechanical protection for the deformable inner container. However, for a device produced in this way to operate, it is necessary for the deformable inner container to be able to retract.
For this reason, it is necessary to allow outside air to enter into the volume delimited between the deformable inner container and the rigid outer container.
This intake of air is generally provided in the bottom of the rigid container in which a passage is provided for this purpose, but the intake of air may also take place in the vicinity of the neck of this rigid container.
The major drawback of this type of packaging device lies in the fact that the deformable inner container, which is manufactured from plastic, must have a thin wall thickness in order to be able to deform easily, and in the fact that this results in considerable permeability of the wall of the deformable container and migration of part of the product and/or evaporation of at least one volatile component of the product to be dispensed through this flexible wall of the deformable container.
This phenomenon may be observed particularly with aqueous or alcoholic products and/or with those containing one or more volatile substances.
A gas released by the packaged product or a vapor resulting from the evaporation of a volatile phase of this product can pass through the thin wall of the deformable container and escape towards the outside via the passage reserved for the air intake.
In order to remedy this drawback, deformable containers made from relatively impermeable flexible composite materials have been proposed.
However, these materials have the disadvantages of being expensive and difficult to employ. Moreover, they are never totally impermeable and migration and/or evaporation is always noted after a reasonably long period.
A further solution to this problem already proposed consists in providing a non-return or one-way valve placed in the passage or downstream of the passage provided for the air intake.
A valve of this type permits passage in one direction only and it allows the air to enter into the volume between the two containers when the suction due to the return of the pump piston towards its rest position, pressing against a stop of the pump body, requires it, but prevents leakage towards the outside of gases and/or vapor, the presence of which in the volume between the two containers is the result of evaporation and of the passage of volatile phase(s) of the product contained in the deformable container through the thin wall of this container.
Thus, evaporation of the product and its migration towards the volume included between the two containers cease as soon as this volume reaches saturation.
However, employing non-return valves of this type requires the manufacture and mounting of at least one additional piece in order to produce this valve, which considerably increases the cost of the device.
A second drawback of this type of packaging device, comprising a manual pump without air intake fitted to an assembly of two containers, one being a deformable inner container and the other a rigid outer container, lies in the cost of manufacturing the deformable container.
The two methods currently used for manufacturing these thin-walled deformable containers are extrusion blow-moulding and injection blow-moulding of plastic.
These two methods do not make it possible to obtain all the desirable shapes of the necks of the containers, nor do they make it possible to obtain pieces at very low prices.